Throttle return spring redundancy system

ABSTRACT

A throttle valve, situated within the induction passage bore of a fuel or air induction device, is carried by a throttle shaft for fixed rotation therewith; a lever fixedly connected to the throttle shaft is operatively connected to a remotely situated operator&#39;&#39;s foot-operated throttle control; a first throttle return spring is operatively connected to the first lever for returning the throttle valve to an idle position whenever the foot-operated throttle control is released; and a second safety spring is provided for assuring the movement of the throttle valve to the idle position in the event that, for example, either the first throttle return spring or the associated throttle control linkage should fail while the throttle valve is in either a partly or fully opened position.

United States Patent Eshelman et a1.

[54] THROTTLE RETURN SPRING REDUNDANCY SYSTEM [72] Inventors: Philip V. Eshelman, Southfield; Roy 0. Erickson, Utica; Keith D. Marsh, St. Clair Shores, all of Mich.

[73] Assignee: Holley Carburetor Company, Warren, Mich.

[22] Filed: June 8, 1971 [21] Appl. No.: 150,997

[52] US. Cl ..123/l98 DB, 123/142, 123/198 D,

123/103 A, 180/82, 74/513 [51] Int. Cl.. ....F02b 77/08, F02d 1 1/04, B60k 22/08 [58] Field of Search ..123/142, 198 D, 198 DB;

[56] References Cited UNITED STATES PATENTS 3,626,919 12/1971 MacMillan ..123/198 DB [451 Oct, 17, 1972 Primary Examiner-Wendell E. Burns Attorney-Walter Potoroka, Sr,

[57] ABSTRACT A throttle valve, situated within the induction passage bore of a fuel or air induction device, is carried by a throttle shaft for fixed rotation therewith; a lever fixedly connected to the throttle shaft is operatively connected to a remotely situated operator's foot-operated throttle control; a first throttle return spring is opera tively connected to the first lever for returning the throttle valve to an idle position whenever the footoperated throttle control is released; and a second safety spring is provided for assuring the movement of the throttle valve to the idle position in the event that, for example, either the first throttle return spring or the associated throttle control linkage should fail while the throttle valve is in either a partly or fully opened position.

15 Claims, 18 Drawing Figures P'A'TE'N'TEDncr 11 I972 SHEET 1 BF 6 g, mm

INVEN TORS ,5 h am m A uaw y PATENTED I972 3,698,372

- saw u or 6 AZT TO RVNEY PATENTEDBBIIT 19 2 3,698,372 SHEET 8 OF 6 I NVENTORS I ATTORNEY THROTTLE RETURN SPRING REDUNDANCY SYSTEM BACKGROUND OF THE INVENTION Heretofore, carburetors or other engine induction devices, employing an induction passage with a throttle valve therein, had a lever fixed to the throttle shaft which lever, in turn, was operatively connected to associated throttle control linkage (as the vehicle operators foot-controlled throttle pedal within the vehicle passenger compartment) and to a return spring for returning the throttle valve to an engine idle position when control over the throttle had been relinquished by the vehicle operator.

Even though such carburetors and induction devices have performed well in the past and have not shown any tendancy to experience failure of such a throttle return spring or the associated throttle control linkage, the Federal Government has, nevertheless, recently issued new proposed safety standards in regard to driveroperated throttle or accelerator control systems.

Such standards, among other things, require that: (l in the event the normal or usual throttle return spring should fail, means must be provided for assuring that the throttle will return to its idle position; and (2) in the event the associated throttle control linkage should fail, means must be provided for assuring that the throttle will return to its idle position.

Accordingly, the invention as herein disclosed is primarily concerned with the solution of the above as well as other related problems.

SUMMARY OF THE INVENTION According to the invention, an automatic throttle return device comprises a first lever adapted for connection to an associated throttle shaft and throttle valve for rotation therewith, first spring means for rotating said first lever and throttle valve to an idle position during normal operating conditions, and second safety spring means energized upon failure of said first spring means for assuring rotation of said first lever and said throttle valve to said idle position.

Various general and specific objects and advantages of the invention will become apparent when reference is made to the following detailed description considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS In the drawings wherein, for purposes of clarity, certain details and elements may be omitted from one or more views:

FIG. 1 is a vertical cross-sectional view of a governed type of carburetor structure employing a first embodiment of the invention;

FIG. 2 is a view taken generally on the plane of line 2-2 of FIG. 1 and looking in the direction of the arrows;

FIG. 3 is a fragmentary perspective view illustrating a portion of a throttle shaft of FIG. 1 along with a primary throttle valve mounted thereon;

FIG. 4 is a fragmentary elevational view of the primary throttle operating lever portion cut away in FIG. 1, as seen when viewed from the left of FIG. 1;

FIG. 5 is a fragmentary elevational view taken generally on the plane of line 5-5 of FIG. 4 and looking in the direction of the arrows;

FIG. 6 is an enlarged fragmentary elevational view of certain of the elements of FIG. 4 showingsuch elements during normal operation;

FIG. 7 is a view similar to FIG. 6 but illustrating the elements in positions assumed resulting from the failure of the normal throttle return spring;

FIG. 8 is a cross-sectional view taken generally on the plane of line 8-8 of FIG. 6 and looking in the direction of the arrows;

FIG. 9 is a fragmentary perspective view illustrating a second embodiment of the invention;

FIG. 10 is an enlarged fragmentary cross-sectional view taken generally on the plane of line 10-10 of FIG. 9 and looking in the direction of the arrows;

FIG. 11 is a fragmentary elevational view taken generally on the plane of line 11-11 of either FIGS. 9 or 10 and looking in the direction of the arrows;

FIG. 12 is a view similar to FIG. 10 but illustrating a third embodiment of the invention;

FIG. 13 is a fragmentary side elevational view of a fourth embodiment of the invention;

FIG. 14 is a top plan view taken generally on the plane of line 14-14 of FIG. 13 and looking in the direction of the arrows;

FIG. 15 is an end elevational view taken generally on the plane of line 15-15 of FIG. l3 and looking in the direction of the arrows;

FIG. 16 is a side elevational view of a fifth embodiment of the invention; v

FIG. 17 is an end elevational view taken generally on the plane of line 17-17 of FIG. 16 and looking in the direction of the arrows; and

FIG. 18 is a top plan view taken generally on the plane of line 18-18 of FIG. 16 and looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in greater detail to the drawings, FIG. 1 illustrates a staged type of four-barrel carburetor having an air intake 12. The carburetor 10 is drawn in sections as to expose one of the primary barrels or induction passeges and one of the secondary induction passages 16. The primary bore or induction passage 14 is provided with a restriction or venturi throat 18 and a conventionally operated throttle valve 20 mounted on the shaft 22 which extends through the other induction passage in which is mounted a throttle valve of a configuration like that of throttle valve 20. The secondary induction passage 16 is also provided with a venturi throat 24 and a throttle valve 26 mounted on the shaft 28 which extends through the other secondary induc tion passage in which is mounted another secondary throttle valve like valve 26.

A vacuum device 30, commonly referred to as a governor diaphragm assembly, is mounted as on a boss 32 extending from the carburetor body 34. The assembly 30 includes a body 36 formed to provide recesses 38 and 40. The recess 40 is covered by means of a flexible diaphragm 42 which is secured to the body 36 by means of a cover member 44 formed to provide an air-tight chamber 46 of which the flexible diaphragm 42 forms a wall. The cover member may be secured by any suitable means such as screws 47.

As shown by FIGS. 1 and 2, the diaphragm 42 has secured to the center thereof in a conventional manner a rod 48 passing through passage 50 in the body 36 and having a laterally extending end 52 pivotally secured to the lever 54 which is rigidly secured to the end 56 of the primary throttle shaft 22 extending into the chamber 38. The shaft 22 is mounted in an anti-friction bearing 39, and a spring 41 is disposed between the bearing pring and the steel and leather washers 43 and 45 to provide a seal. A tension spring 58 attached between the adjustable pin 60, mounted in one of the holes 62 in the body 36, and the fixed pin 64, secured to the lever 64, tends to hold the primary throttle plate or valve 20 in the open position. An atmospherically vented cover plate 66 may be secured by screws 68 to housing 36, thereby protecting the mechanism within chamber 38.

The orifice 72 at the primary venturi throat 18 and the orifice 74 below the primary throttle valve 20 are connected by means of the passages 76 and 78 having fixed restrictions 80 and 82, respectively, with the passage 84 in body member 36 and the passage 86 in the cover member 44 which lead to the chamber 46. A passage 88 connected with passage 84 terminates in an opening in the body 36 adapted to receive a threaded fitting 90.

I Located at any desired position on the engine is a governor valve assembly 92 comprising a stationary housing 94 adapted to be mounted on the engine and containing a shaft 96 driven in any suitable manner in proportion to, for example, engine or vehicle speed. Mounted for rotation with the shaft 96 is a laterally extending sleeve 98 having a spring 100 mounted within the axial passage 102 in the sleeve by attachment at one end to the internally threaded member 104, which is keyed in passage 102. Spring 100 is adjustable axially of sleeve 98 by turning the adjustment screw 106 which is reached by removing the access screw 108. The other end of the spring 100 is secured to the governor weight 110 movable axially within the chamber 112 against the spring 100 and having at the free end thereof a valve 114 adapted to close the orifice 116 when the weight 110 is forced outwardly due to the rotation of the shaft 96 and the sleeve 98 in accordance with engine speed. The engine or vehicle speed at which the orifice 116 will be closed is dependent, of course, upon the adjustment of the spring 100. It is apparent, also, that some other governor valve structure may be employed.

A vacuum balancing air bleed is provided through assembly 92 to chamber 46 when orifice 116 is uncovered. Conduit 118 between the air intake 12 of the carburetor and the housing 94 and conduit 122 between the engine or vehicle is operating at a speed insufficient to close the orifice 116, the engine vacuum will draw clean air through the conduit 118, into the housing 94, through the orifice 116 and into the chamber 112, through the passage 102 and the axial passage 120 in the shaft 96 and thence through the conduit 122 to the governor diaphragm assembly 30. When the engine reaches governed speed, the orifice 116 is closed and the air bleed through conduit 122 is cut off. When this occurs, vacuum in the chamber 46 urges the diaphragm 42 downwardly, as in FIG. 2, against the spring 68 to close the primary throttle valves 20.

A secondary throttle diaphragm assembly 124 is mounted at the opposite side of the throttle body 34. This assembly comprises a body 126 having a recess 128 vented to the atmosphere through a plate 130 secured by screw 132 and a recess 134 closed by a flexible diaphragm 136 which is secured to the body 126 by means of a cover 138 formed to provide oppositely disposed chambers 140 and 142 between which the flexible diaphragm 136 forms a movable wall. The chamber 142 contains a compression spring 144 positioned between the cover 138 and the arm 146, which is secured to the center of the diaphragm 136, so that the spring 144 urges the arm 146 upwardly to rotate the lever 148 secured rigidly to the secondary throttle shaft 28 counter-clockwise, as when viewed from the left in FIG. 1, and thereby close the secondary throttle valves 26. A conduit 150 extending between the chamber 142 and the vacuum passages 152 and 154 opening to the primary and secondary venturi throats 18 and 24 enables primary and/or secondary venturi vacuum to evacuate the chamber 142 and displace the diaphragm 136 downwardly, as in FIG. 1, against the spring 144 to open the secondary throttle 26. The rate of the spring 144 is selected so that the secondary throttle valve 26 will be open at any predetermined venturi vacuum.

FIG. 3, in fragmentary perspective view illustrates a portion of the throttle shaft 22, as it may extend through a wall of the carburetor 10, with one of the primary throttles 20 mounted thereon for rotation therewith. A clutching device is illustrated as comprising a first lever-like member 162 fixedly secured to the end of the primary throttle shaft 22 and a cooperating second lever-like member 164 fixedly secured to a stub-shaft 166 which is suitably journalled so as to be preferably axially aligned with shaft 22. Lever member 162 includes a generally laterally extending arm portion 168 which is so positioned as to be in the general path of travel of a second projecting arm portion 170 carried by member 164 so that when shaft 166 is rotated in the direction indicated by arrow 172 arm portion 170 will engage arm portion 168 and cause rotation of primary throttle valve 20 in the direction indicated by arrows 174. The other end of throttle actuating shaft 166 is connected to the safety throttle return device 176 of FIGS. 4, 5, 6, 7 and 8.

Referring first to FIG. 8, it can be seen that the throttle return device 176 is shown as being comprised of a first lever 178 having a mounting aperture 180 by which it is mounted onto shaft 166 and secured thereto for rotation therewith as by keying flatted portions 182 formed on the shaft 166 and cooperating flatted portions 184 formed in the aperture 180 of lever 178. A pivot pin 186, which may be pressed into an aperture 188 of lever 178 as to be secured thereto, pivotally supports a latching lever 190 which, in turn, as shown in FIGS. 4 and 6 has its other end operatively connected to a throttle return tension spring 192 having its opposite end suitably anchored as at 194.

A second latching or throttle control lever 196 is preferably fixedly secured to a bushing 198 which in turn is freely received on a necked-down portion 200 shaft 166 so as to be rotatable with respect thereto. A drumlike member 202 is also freely journalled on the reduced diameter 200 of shaft 166 and axially retained thereon as by a washer or thrust bearing 204 and a C- clip 206. The drum 202 serves to generally carry and retain a coiled tosion safety spring 208 thereabout.

As best seen in FIG. 5, levers 178 and 196 are respectively provided with generally laterally extending arm portions 210 and 212 to which are operatively connected hooked ends 214 and 216 of torsion spring 208 so as to result in lever 178 being urged counterclockwise and lever 196 being urged clockwise as viewed in, for example, either FIGS. 4 or 6.

Another arm portion 218 of lever 196 is pivotally connected to one end 220 of a motion transmitting member such as a rod 222 which, in turn, is operatively connected as to the foot operated throttle control lever or pedal 224 within the vehicle passenger compartment.

As best shown in FIGS. 5 and 8, it can be seen that the main body portion of levers 190 and 196 are substantially in the same plane. This is done to enable such levers to coact with each other as by having a tonguelike latching projection 226 formed on lever 190 received within a cooperating recess or slot 228 formed in lever 196.

For the moment neglecting the latching projection 226 and recess 228, it can be seen that the only lever which is in any way fixed or secured for driving rotation of the primary throttle valve is lever 178 because lever 196 is rotatable with respect to shaft 166 and lever 190 is pivotally carried by lever 178.

OPERATION OF INVENTION For purposes of description, let it be first assumed that the elements are in the respective positions as shown in FIGS. 4 and 6. At this time the throttle valves 20 will be in their normally closed or curb idle position within induction passages 14 as generally depicted in, for example, FIG. 4. Also, as illustrated in FIG. 6, the torsion safety spring 208 is attempting or urging the levers 178 and 196 in the directions previously described but is precluded from so moving the levers because of projection 226 being engaged within latching recess 228. This engagement between member 226 and recess 228 is maintained by the spring 192 which also serves to provide the force for returning the shaft 166, shaft 22 and throttle valve 20 to the curb idle position.

During normal operation when opening movement of the throttle valve 20 is desired, foot-operated throttle pedal 224 is rotated counter-clockwise about its pivot support 230 causing rod or linkage 222 to move to the left, as viewed in FIGS. 4 or 6, which, in turn, causes clockwise rotation of lever 196. As lever 169 is so rotated, it, through latched recess 228 and projection 226 causes like rotation of latching lever 190 translationally about the center of axis of shaft 166. Such rotation of latching lever 190, in turn, imparts rotation to lever 178 through the interconnecting pivot member 186. Of course, since lever 178 is fixedly secured to shaft 166 for rotation therewith, clockwise rotation of lever 178 allows clockwise rotation of the shaft 166, shaft 22 and primary throttle valve 20 in the opening direction as urged by spring 58 in FIG. 1 and 2.

When throttle control pedal 224 is released, the return spring 192 pulls at the upper end of lever 190 causing counter-clockwise rotation thereof as well as like rotation of levers 178 and 196. This, in turn, results in shafts 166 and 22 also turning counter-clockwise with throttle valve 20 being returned to the curb idle position. In the particular embodiment of carburetor disclosed, the spring 58 of FIG. 2 actually supplies the force for opening the throttle valve 20.

Further, as is generally well known in the art a suitable throttle stop screw 232 may be provided as generally depicted in FIG. 7. The screw 232 may be threadably carried by an arm portion 234 of a lever-like member 236 suitably fixedly secured to the throttle operating shaft 166 so as to rotate therewith. The purpose of such a stop screw is, of course, to coact with a suitable abutment 238 and in so doing determine the curb idle position of the throttle valve 20.

Let it now be assumed that throttle rod 222 has causedclockwise rotation of levens 196, 178 and to a position where, for example, the throttle valve 20 is approaching a wide open position. Further, let it be assumed that at that moment the throttle return spring 192 breaks. If this were to happen the throttle 20 would be returned to a safe engine operating position and not remain in its nearly wide open portion at which point the spring 192 broke. This would occur as follows. It should 'be noted that the sides of the notch or slot 228 are made slightly tapered as are the juxtaposed sides of the latching projection 226. Consequently, the torsional force of torsion spring 208 continually urges the projection 226 out of seated engagement with the slot or recess 228. However, in normal operation return spring 192 provides enough force to prevent disengagement between latching portions 226 and 228. Therefore, if return spring 192 should break, the force of the torsionsafety spring 208 forces the latch tongue 226 out of engagement with latch slot 228. With the latching means thusly disengaged, the torsion safety spring 208 causes the throttle shaft lever 178 to start to rotate counter-clockwise while at the same time urging the throttle linkage lever 196 to rotate in the clockwise direction. The throttle shaft lever 178 will rotate in the counter-clockwise direction until the related throttle stop screw, such as screw 23.2, abuts against its cooperating abutment whether it be a related fast idle cam or a fixed stop as 238 which, in either case, determine the curb idle position of the throttle valve 20.

When the throttle lever 178 has been so rotated resulting in a curb idle position for the throttle valve 20, the safety torsion spring 208 is able to exert its remaining full force against throttle linkage lever 196 so as to cause it to rotate clockwise to the position shown in FIG. 7 whereat the throttle linkage 222 is moved so far to the left as to cause counter-clockwise rotation of the foot pedal 224 to a degree rendering the pedal 224 useless for operation of the throttle 20. That is, for practical purposes, all possible motion of the foot pedal 224 in the throttle-opening direction is taken-up by the rotation of lever 196.

The same results would also occuras set forth above if, instead of assuming that the throttle return spring 192 broke, the linkage 222 interconnecting the lever 196 and foot pedal 224 were to break.

In view of the above, it can be seen that the invention as herein disclosed provides means effective for assuring the closure of the throttle valves whenever either the throttle actuating linkage, such as 222, or the throttle return spring 192 should fail thereby preventing the occurrence of a runaway engine with a throttle valve stuck in either a partly or wide open position.

SECOND EMBODIMENT OF THE INVENTION FIGS. 9, l and l 1 illustrate a second embodiment of the invention as comprising a first lever 250 axially retained on a throttle shaft 252, in a manner to permit the free angular rotation therebetween, and a second lever 254 which is suitably fixedly secured to throttle shaft 252 for rotation therewith. A coiled torsion spring 256 is situated generally about throttle shaft 252 and between levers 250 and 254 in a manner as to have spring arms 258 and 260 hooked onto the levers continually urging lever 250 clockwise, as viewed from end 262 of shaft 252, and lever 254 counter-clockwise.

The upper ends of levers 250 and 254 are respectively provided with apertures 264 and 266 which slideably receive therethrough a laterally projecting portion 268 of a throttle linkage control element 270. As also illustrated in FIG. 10, a coiled compression spring 272 is situated about lateral projection 268 so as to have one end thereof abutting against lever 254 which the other end is seated against an abutment washer 274 secured against axial movement as by a cross pin 276 passing through lateral projection 268. Accordingly, it can be seen that spring 272, which is a relatively weak spring, continually urges lateral portion 268 to the left, as viewed in FIG. 10, thereby tending to move the lateral projection 268 out of engagement with aperture 266 of lever 254. However, end 278 of linkage 270 extending beyond lever 254 is provided with a recess or groove 280 formed therein which rather loosely receives one end of an abutment linkage or member 282. As best seen in FIGS. 9 and 11, the abutment 282 is provided with a slot 284 formed therein which is received generally within the groove 280. The other end of abutment 282 is connected to a relatively strong throttle return spring 286 which may be anchored as at 288. The edges of the groove 280 as well as the edges defining the slot 284 in abutment 282 may be suitably contoured as to provide a camming action therebetween which, due to the force of spring 272, tends to cause disengagement between abutment 282 and end 278 of lateral extension 268. However, during normal operating conditions, the force of throttle return spring 286 is sufficient to overcome the said camming action and maintain abutment member 282 in engagement with end 278. As long as such engagement is maintained abutment member 282 prevents the withdrawal of end 278 through aperture 266 of lever 254. Because of the preferred looseness of the connection between lateral projection 268 and apertures 264, 266, a laterally extending abutment arm 286 may be provided on lever 250 as to thereby engage lever 254 during normal operation.

The throttle valve 290 is illustrated in its nominally closed or curb idle position and its movement in the opening direction is depicted generally by the arrows 292. The normal temperature curb idle position may be determined as by a threadably adjustable idle stop screw 294, carried as by a lug 296 formed on the carburetor body, and a generally downwardly depending abutment portion 298 formed on lever 254. A second stop portion 300, which may also be formed on the carburetor body, serves as a maximum throttle opening stop against which a generally downwardly depending abutment portion 302, formed on lever 250, is adapted to abut thereby determining the nominally wide-openthrottle position.

As somewhat schematically illustrated in FIG. 9, the opposite end of throttle linkage means 270 is pivotally connected as at 304 to a lever 306 which has its other end pivotally connected as at 308 to a linkage 310. An operator foot controlled lever or pedal 312 is pivotally connected at generally its opposite ends to a suitable base or support 314 and to the linkage 310.

OPERATION OF SECOND EMBODIMENT With the elements in the respective positions shown in FIG. 9, as pedal 312 is rotated counter-clockwise about pivot connection 316, lever 306 is also rotated counter-clockwise causing throttle linkage 270 to move generally to the right. Such movement of linkage 270 causes both levers 250 and 254 to rotate clockwise thereby rotating throttle shaft 252 and throttle valve 290 in the opening direction as generally depicted by the arrows 292. g

The above described movement of the elements, is of course, resisted by the throttle return spring 286 continually tending to return the throttle valve 290 to the curb idle position illustrated. Accordingly, it should be evident that if for some reason the throttle linkage 270 (or other linkages associated therewith) should break or in any way experience a failure, the throttle return spring 286 will rotate levers 250 and 254 counterclockwise until abutment 298 engages stop screw 294 thereby returning the throttle valve 290 to its curb idle position.

Now, let it be assumed that the throttle valve 290 has been rotated to some partly opened position and that, with the throttle valve in such position, the return spring 286 for some reason fails. At this point, it should be stated that in the preferred form of the second embodiment, the torsion or safety spring 256 is of a substantially greater force than that exhibited by return spring 286.

As the throttle return spring 286 fails, the latch member 282 is permitted to fall causing its slotted end portion 284 to disengage itself from the recess 280. This, in turn, permits coiled compression spring 272 to move lateral extension 268 of linkage 270 to the left (as viewed in FIG. 10) causing end 278 thereof to be withdrawn from aperture 266 of throttle lever 254.

As soon as end 278 is thusly withdrawn torsion safety spring 256 causes relative rotation as between levers 250 and 254. That is, as viewed in FIG. 9, arm 260 of spring 256 tends to rotate lever 254 counter-clockwise, while arm 258 of spring 256 tends to rotate lever 250 clockwise. It should be evident that such relative rotation of levers 250 and 254 will continue until abutment portion 298 of lever 254 strikes and comes to rest against stop screw 294 and abutment portion 302 of lever 250 strikes and comes to rest against maximum throttle stop portion 300 at which time throttle valve 290 will have been rotated to its curb idle position shown. In the embodiment shown, once lever 250 has been rotated to abutting engagement with maximum stop 300, throttle pedal 312 will also have been rotated to a position corresponding to a wide-open-throttle position thereby indicating to the vehicle operator that a failure of some kind has occurred in the throttle operating mechanism.

Accordingly, in view of the above, it can be seen that the second embodiment of the invention provides apparatus which upon failure of the throttle control linkage means, such as at 270, causes rotation of the throttle valve 290 to its idle position through the action of return spring 286; the apparatus is also effective upon failure of the return spring 286 to, through the action of safety spring 256, return the throttle 290 to its idle position while simultaneously causing rotation of the throttle foot control 312 as a signal to the vehicle operator.

THIRD EMBODIMENT OF THE INVENTION FIG. 12 illustrates a third embodiment of the invention. All elements therein which are the same as those of FIGS. 9, l and 11 are identified with like reference numbers.

The embodiment of FIG. 12 contemplates a structure identical to that of FIGS. 9, and 11 is replaced by a basically identical linkage means 270a which has its lateral extension 268a inserted through levers 254 and 250 from a direction reverse to that of FIGS. 9, 10 and 11.

OPERATION OF THIRD EMBODIMENT The overall operation of the third embodiment is like that of the second embodiment, previously described, with the following noted exceptions.

If it is assumed that return spring 286 should fail which the throttle valve 290 is in some opened position, lateral extension 2680 will slide out of aperture 264 of lever 250 (which is otherwise freely rotatable with respect to shaft 252) but remain within aperture 266 of lever 254 (which is fixedly secured to shaft 252 for rotation therewith). Consequently, lever 250 under the action of safety spring 256 rotates (clockwise as viewed in FIG. 9) until it strikes maximum stop or abutment 300 where it will remain. With linkage means 270a still in operative engagement with lever 254, the operator can still exercise control over the throttle valve 290.

However, in the third embodiment, safety spring 256 is selected so as to have a significantly greater spring pre-load force, at the time that lever 250 abuts against stop 300, than that exhibited by the normal return spring 286. Consequently, the operator, even though still able to control the position of the throttle valve 290, has to suddenly exhert a substantially greater force against the throttle foot control 312 in order to achieve movement thereof. Such change in required operating force serves as a signal to the vehicle operator that a malfunction has occurred without depriving the operator of the ability to drive the vehicle especially important where such malfunction possibly occurred in a dangerous area of the roadway.

FOURTH EMBODIMENT OF THE INVENTION FIGS. 13, 14 and 15 illustrate a fourth embodiment of the invention as comprising a first lever 350 suitably fixedly secured, as by spot welding, to a throttle shaft 352 for rotation therewith, and a second lever 354 carried by the throttle shaft a manner permitting relative rotation between shaft 352 and lever 354. A throttle valve 356, located as within the induction passage bore 358, is carried by the throttle shaft 352 for rotation therewith.

A throttle control rod or linkage 360 has one end 362 pivotally connected to arm portion 364 of lever 350 while its other end is pivotally connected as at 366 to a lever 368 which, in turn, has its other end pivotally connected as at 370 to a motion transmitting linkage 372 pivotally carried by or connected to the vehicle operators foot actuated throttle pedal 374.

As best seen in FIGS. 13 and .14, the opposite arm portion 376 of lever 250 is provided with a transversely extending tab-like portion 378 through which is formed an aperture 280 which is large enough to freely accept therethrough the shank portion 382 of a latching linkage 384 but not a head portion 386 formed at the end thereof.

An open-ended slot 388, formed near the end of lever 354, permits the passage or extension therethrough of the linkage 384. The free end of linkage 384 is preferably formed with a hook-like portion 390 to which one end 392 of a throttle return spring 394 is attached. The other end 396 of spring 394 is suitably anchored as at 398. As best seen in FIGS. 14 and 15, lever 354 also carries a laterally extending tablike abutment 400 which extends generally under arm portion 376 of lever 350. An annular spacer 402 may be provided between lever 354 and a washer 404 both of which are axially retained on shaft 352 as by a nut 406 engaged to a threaded portion 408 of shaft 352.

A safety torsion spring 410 carried generally about shaft 352 and between levers 350 and 354 has arm portions 412 and 414 respectively hooked over the levers as to continuously urge lever 350 in a clockwise direction and lever 354 in a counter-clockwise direction as viewed in FIG. 13.

OPERATION OF FOURTH EMBODIMENT As should be apparent, the tension of return spring 394 exerts a force through the leverage action of link age 384 to force the lower edge of arm portion 376, of lever 350, against the upper surface of abutment tab 400 thereby keeping levers 350 and 354 effectively abutably engaged to each other and assuring unison of movement therebetween.

When during normal operation the levers 350 and 354 respond to the action of return spring 394, they both are caused to rotate clockwise; thereby rotating throttle shaft 352 and throttle valve 356 in the closing direction, until lever arm portion 364 abuts against the adjustable idle stop screw 416 assuming positions as illustrated in FIG. 13.

Let it be assumed that through the action of throttle foot control 374 and linkage 360, levers 350 and 354 have been rotated counter-clockwise some degree thereby causing the throttle valve 356 to correspondingly become partly opened. If at this time return spring 394 should fail, the latch linkage 384 will be released permitting levers 350 and 354 to function independently of each other. Accordingly, safety torsion spring then causes lever 354 to rotate counterclockwise until it strikes and comes to rest at against the maximum throttle stop 418 as illustrated at 4540 of FIG. 13. When this happens, the remaining force of torsion spring 410 is applied against arm 364 of lever 350 so as to provide a throttle return or closing force thereto tending to rotate lever 350 and throttle 356 toward the idle position as determined by the adjustable stop 416. Preferably, the torsion spring 410 has a substantially greater spring pre-load force than return spring 394 thereby creating a signal to the vehicle operator that a malfunction had occurred much in the same manner as that discussed with reference to FIG. 12.

Of course, if at the previously assumed part throttle position the linkage from lever 350 to foot throttle control 374 should fail, return spring 394 would rotate levers 354, 350 and throttle valve 356 to the idle position shown in FIG. 13. Further, on the off-chance that both the throttle control linkage and return spring 394 should fail, safety torsion spring 410 would still rotate lever 354 to position 354a and rotate lever 350 to the idle position against stop 416.

FIFTH EMBODIMENT OF THE INVENTION FIGS. 16, 17 and 18 illustrate a fifth embodiment of the invention as comprising a first lever 450 suitably fixedly secured to a throttle shaft 452 for rotation therewith. A throttle valve 454, located as within the induction passage bore 456, is also secured to and carried by the throttle shaft 452 for rotation therewith.

Lever 450 is also provided with a preferably integrally formed drum portion 458 about which is carried a torsion safety spring 460 which has one end 4'62 received within a slot or recess 464 formed in drum 458.

A second lever 466 is carried by lever 450 and pivotally secured thereto as by a pivot member 468. Lever 466 is provided with an outwardly extending arm 474 of torsion spring 460. As best seen in FIGS. 16 and 17, levers 450 and 466 are provided with open-ended slots 476 and 478 which collectively receive therethrough one end 480 of a throttle return spring 482 which has its other end 484 suitably anchored as at 486.

A second aperture 488 formed through lever 450 receives one end 490 of a throttle control linkage 492 which has its other end pivotally connected as at 494 to a foot controlled throttle lever or pedal 496 pivotally anchored as at 498.

OPERATION OF FIFTH EMBODIMENT The various elements shown in FIGS. 16, 17 and 18 are illustrated in positions corresponding to curb idle throttle position. Generally, as foot control 496 is rotated clockwise about anchor pivot 498, linkage 492 causes corresponding clockwise rotation of lever 450 and throttle shaft 452 along the throttle valve 454. At this time the second lever 466, while maintaining its position relative to lever 450, is carried by lever 450 as it rotates about the axis of shaft 452. The relative position of second lever 466 is maintained by virtue of return spring 482 continually exhibiting a return force against both levers 450 and 466. The effective force of return spring 482 is sufficient to overcome the tendency of arm 474 of torsion safety spring 460 to rotate the second arm 466 clockwise about pivot support 468. With continued clockwise motion of control pedal 496,

lever 450 eventually abuts against surface 500 of a positive stop 502 which serves to determine the maximum or wide open throttle position.

If during wise open throttle engine operation (or at some partly opened throttle position) the control linkage 492 should experience a failure, throttle return spring 482 will, of course, cause counter-clockwise rotation of lever 450 until the elements return to the curb idle positions shown in FIG. 16.

However, if, for example, during wide open throttle operation the normal throttle return spring 482 should fail, arm 474 of safety torsion spring 460 is permitted to rotate second lever 466 clockwsie about pivot 468. Such rotation of secondlever 466 continues until it strikes and comes to rest against surface 500 of maximum stop 502. However, the reaction force of safety spring 460, still tending to cause further coiling of arm 474 about drum 458, results in end 462 of spring 460, engaged in slot 464, causing counter-clockwise rotation of drum 458 and lever 450 along with throttle valve 454 continues until such elements again reach the curb idle positions shown in FIG. 16.

GENERAL DISCUSSION In view of the preceding, it can be seen that the various embodiments of the invention, herein disclosed, provide a safety system for assuring the return of the throttle valve to an idle position regardless of whether the associated throttle control linkage or the normal throttle return spring should fail.

Even though the invention has been disclosed in connection with a throttle valve, as employable in various forms of fuel control devices, it should be apparent that the invention can be practiced or employed equally well in an environment wherein assurance is required that a particular moveable element is always returned to a predetermined position should the associated normal control and return mechanism experience a failure.

Although only a select number of embodiments of the invention have been disclosed and described, it is apparent that other embodiments and modifications of the invention are possible within the scope of the appended claims.

We claim:

1. Apparatus for assuring the return from a partly opened or fully opened position of a throttle valve to an idle position, comprising a shaft rotatable in accordance with the rotation of said throttle valve, a lever carried by said shaft for rotation therewith, manually actuated throttle control linkage means operatively connected to said lever for at times effecting rotation of said shaft and said throttle valve in the throttle opening direction, first spring means operatively connected to said shaft and throttle valve for continually applying a resilient force thereagainst in a direction opposite to said throttle direction in order to at times rotate said shaft and said throttle valve to said idle position, second pre-loaded spring means operatively connected to said lever, and latch type restraining means for preventing said second spring means from causing rotational motion of said lever during normal operation of said first spring means, said latch type restraining means being disengaged and effective upon failure of said first spring means to permit said second spring means to resiliently urge said lever and throttle valve to said idle position.

2. Apparatus according to claim 1, wherein said latch type restraining means comprises a second lever secured to said throttle control linkage means and freely rotatable about said shaft, a third lever pivotally connected to said first mentioned lever, a first latching surface formed on said second lever, a second latching surface formed on said third lever and adapted for cooperative engagement with said first latching surface, wherein said first spring means is operatively connected to said third lever for urging and maintaining said first and second latching surfaces in cooperative engagement as long as said first spring does not experience a failure, and wherein said second spring means operatively engages said first mentioned lever and said second lever in a manner continually urging said first mentioned lever and said second lever to experience relative rotation with respect to each other.

3. Apparatus according to claim 2, wherein said throttle control linkage means is operatively connected to said first mentioned lever by being directly connected to said second lever and thereby drivingly connected to said first mentioned lever through said latching surfaces and said third lever, and wherein said second spring means comprises a coiled torsion spring having one arm thereof engaged with said first mentioned lever and a second arm thereof engaged with said second lever.

4. Apparatus according to claim 2, wherein said latching surfaces are cammed with respect to each other thereby continually tending to disengage from each other under the influence of said second spring means.

5. Apparatus according to claim 2, wherein said throttle control linkage means is operatively connected to said first mentioned lever by being directly connected to said second lever and thereby drivingly connected to said first mentioned lever through said latching surfaces and said third lever, wherein said second spring means comprises a coiled torsion spring having one arm thereof engaged with'said first mentioned lever and a second arm thereof engaged with said second lever, and wherein said latching surfaces are cammed with respect to each other thereby continually tending to disengage from each other under the influence of said coiled torsion spring.

6. Apparatus according to claim 1, wherein said latch-type restraining means comprises a second lever carried by and freely rotatable about said shaft and a portion of said throttle control linkage means extending through said second lever and said first mentioned lever, resilient means continually urging said portion of said throttle control linkage means out of engagement with one of said levers, abutment means for preventing said resilient means from moving said portion of said throttle control linkage means out of engagement with said one of said levers during normal operation of said first spring means, wherein said first spring means is operatively connected to said abutment means for applying therethrough said force tending to return said shaft and throttle valve to said idle position and to maintain operative engagement between said portion of said throttle control linkage means and said abutment means, wherein said second spring means operatively engages and continually tends to rotate said first mentioned lever and said second lever relative to each other, and wherein said abutment means is effective upon said first spring means experiencing a failure to disengage said portion of said throttle control linkage thereby permitting said resilient means to disengage said portion of said throttle control linkage from said one of said levers, and said second spring means being effective upon disengagement of said portion of said throttle control linkage from said one of said levers to cause said relative rotation between said levers and to rotate said first mentioned lever .and throttle valve to said idle position.

7. Apparatus according to claim 6, wherein said one of said levers comprises said first mentioned lever.

8. Apparatus according to claim 6, wherein said one of said levers comprises said first mentioned lever, wherein said second lever includes a generally transversely extending abutment arm carried thereby so as to be adapted for at times abuttingly engaging said first mentioned lever, and wherein said second spring means comprises a coiled torsion spring having a first arm portion engaging said first mentioned lever and a second arm portion engaging said second lever.

9. Apparatus according to claim 6, wherein said second spring means is of a preload and rating sufficient to exhibit a greater force to return said shaft and throttle to said idle position than that exhibited by said first spring means.

10. Apparatus according to claim 1, wherein said latch-type restraining means comprises a second lever carried by and freely rotatable about said shaft, a linkage member connected to said first mentioned lever, wherein said first spring means :is connected to said linkage member in order to yieldingly urge said linkage member in one direction, wherein said second lever is in operative engagement with said. linkage member in a manner resulting in said first mentioned lever and said second lever being urged in rotative motion relative to each other, abutment means carried by one of said levers to prevent said relative rotative motion, wherein said first spring means is effective during normal operation to exert a resilient return force against said linkage member in order to rotate said linkage member said levers and said throttle valve to said idle position.

11. Apparatus according to claim 10, wherein said linkage member is pivotally connected to said first mentioned lever, wherein said second lever includes a slot-like opening formed therein for the reception therethrough of said linkage member, and wherein said second spring means comprises a coiled torsion spring situated generally between said levers and having opposite arm-like end portions respectively engaged with said levers.

12. Apparatus according to claim 1, including a second lever pivotally carried by said first mentioned lever, wherein said second spring means is carried by said first mentioned lever in a manner so as to have one end of said second spring means operatively engaged with said first mentioned lever and a second end operatively engaged with said second lever so as to tend to cause said second lever to pivotally rotate on said first mentioned lever, and wherein said latch-type restraining means comprises a recess formed through said second lever and said first mentioned lever, said recess being formed at a distance from pivot means pivotally connecting said second lever to said first mentioned lever, and including a restraining portion carried by said first spring means for engaging said recess thereby providing a resilient force to said first mentioned lever tending to rotate said first mentioned lever and said throttle valve to said idle position and at the same time preventing pivotal rotation of said second lever about said pivot means, said second end of said second spring means being effective upon failure of said first spring means to cause pivotal rotation of said second lever about said second pivot means until said second lever strikes an associated abutment and then being effective to apply a torsional reaction force against said first mentioned lever in order to urge said first mentioned lever and said throttle valve to said idle position.

13. Apparatus according to claim 1, wherein said second spring means is of a preload and rating sufficient to exhibit a greater force to return said shaft and throttle to said idle position than that exhibited by said first spring means.

14, A carburetor for an internal combustion engine, comprising a carburetor body, an induction passage formed through said body, throttle shaft means extending through said induction passage and journalled for rotation in said carburetor body, a throttle valve situated within said induction passage and carried by said shaft means for rotation therewith, a first lever fixedly secured to said shaft means for rotation therewith, a first pivot member carried by said first lever and extending generally parallel to said shaft means, a second lever carried by said shaft means in a manner permitting said second lever to be freely rotatable with respect to and about said shaft means, a third lever pivotally connected to said first pivot member so as to at least have one end freely swingable thereabout, a generally cylindrical drum carried by said shaft means, manually actuated throttle control linkage means pivotally connected to said second lever, a first latching surface formed on said second lever, a second latching surface formed on said third lever, a first throttle return spring connected to said one end of said third lever, said first throttle return spring being normally effective to cause operative engagement between said first and second latching surfaces in order to effectively lock said second and third levers to each other, said first throttle return spring being further normally effective to rotate said shaft means and said throttle valve to an idle position whenever control over said shaft means and throttle valve is relinquished by said manually actuated throttle control linkage means, coiled torsion spring means carried generally about said drum, said coiled torsion spring means having a first arm portion operatively engaged to said first lever and a second arm portion operatively engaged to said second lever, said torsion spring being further effective to continually urge against the effective resistance of said first spring the disengagement of said second and third levers from each other, and said torsion spring being further effective upon failure experienced by said first spring to cause relative rotation between said first and second levers in order to thereby cause rotation of said shaft means and said throttle valve to said idle position.

15. A carburetor according to claim 14, wherein said shaft means comprises first and second shaft portions, wherein said throttle valve is carried by said first shaft portion, wherein said first and second levers are carried by said second shaft portion, including clutch means carried by said first and second shaft means for effecting driving engagement therebetween, and including means responsive to engine speed operatively connected to said first shaft portion, said means responsive to engine speed being effective upon attainment of a predetermined engine speed to rotate said first shaft portion and said throttle valve some distance toward said idle position. 

1. Apparatus for assuring the return from a partly opened or fully opened position of a throttle valve to an idle position, comprising a shaft rotatable in accordance with the rotation of said throttle valve, a lever carried by said shaft for rotation therewith, manually actuated throttle control linkage means operatively connected to said lever for at times effecting rotation of said shaft and said throttle valve in the throttle opening direction, first spring means operatively connected to said shaft and throttle valve for continually applying a resilient force thereagainst in a direction opposite to said throttle direction in order to at times rotate said shaft and said throttle valve to said idle posiTion, second pre-loaded spring means operatively connected to said lever, and latch type restraining means for preventing said second spring means from causing rotational motion of said lever during normal operation of said first spring means, said latch type restraining means being disengaged and effective upon failure of said first spring means to permit said second spring means to resiliently urge said lever and throttle valve to said idle position.
 2. Apparatus according to claim 1, wherein said latch type restraining means comprises a second lever secured to said throttle control linkage means and freely rotatable about said shaft, a third lever pivotally connected to said first mentioned lever, a first latching surface formed on said second lever, a second latching surface formed on said third lever and adapted for cooperative engagement with said first latching surface, wherein said first spring means is operatively connected to said third lever for urging and maintaining said first and second latching surfaces in cooperative engagement as long as said first spring does not experience a failure, and wherein said second spring means operatively engages said first mentioned lever and said second lever in a manner continually urging said first mentioned lever and said second lever to experience relative rotation with respect to each other.
 3. Apparatus according to claim 2, wherein said throttle control linkage means is operatively connected to said first mentioned lever by being directly connected to said second lever and thereby drivingly connected to said first mentioned lever through said latching surfaces and said third lever, and wherein said second spring means comprises a coiled torsion spring having one arm thereof engaged with said first mentioned lever and a second arm thereof engaged with said second lever.
 4. Apparatus according to claim 2, wherein said latching surfaces are cammed with respect to each other thereby continually tending to disengage from each other under the influence of said second spring means.
 5. Apparatus according to claim 2, wherein said throttle control linkage means is operatively connected to said first mentioned lever by being directly connected to said second lever and thereby drivingly connected to said first mentioned lever through said latching surfaces and said third lever, wherein said second spring means comprises a coiled torsion spring having one arm thereof engaged with said first mentioned lever and a second arm thereof engaged with said second lever, and wherein said latching surfaces are cammed with respect to each other thereby continually tending to disengage from each other under the influence of said coiled torsion spring.
 6. Apparatus according to claim 1, wherein said latch-type restraining means comprises a second lever carried by and freely rotatable about said shaft and a portion of said throttle control linkage means extending through said second lever and said first mentioned lever, resilient means continually urging said portion of said throttle control linkage means out of engagement with one of said levers, abutment means for preventing said resilient means from moving said portion of said throttle control linkage means out of engagement with said one of said levers during normal operation of said first spring means, wherein said first spring means is operatively connected to said abutment means for applying therethrough said force tending to return said shaft and throttle valve to said idle position and to maintain operative engagement between said portion of said throttle control linkage means and said abutment means, wherein said second spring means operatively engages and continually tends to rotate said first mentioned lever and said second lever relative to each other, and wherein said abutment means is effective upon said first spring means experiencing a failure to disengage said portion of said throttle control linkage thereby permitting said resilient means to disengaGe said portion of said throttle control linkage from said one of said levers, and said second spring means being effective upon disengagement of said portion of said throttle control linkage from said one of said levers to cause said relative rotation between said levers and to rotate said first mentioned lever and throttle valve to said idle position.
 7. Apparatus according to claim 6, wherein said one of said levers comprises said first mentioned lever.
 8. Apparatus according to claim 6, wherein said one of said levers comprises said first mentioned lever, wherein said second lever includes a generally transversely extending abutment arm carried thereby so as to be adapted for at times abuttingly engaging said first mentioned lever, and wherein said second spring means comprises a coiled torsion spring having a first arm portion engaging said first mentioned lever and a second arm portion engaging said second lever.
 9. Apparatus according to claim 6, wherein said second spring means is of a preload and rating sufficient to exhibit a greater force to return said shaft and throttle to said idle position than that exhibited by said first spring means.
 10. Apparatus according to claim 1, wherein said latch-type restraining means comprises a second lever carried by and freely rotatable about said shaft, a linkage member connected to said first mentioned lever, wherein said first spring means is connected to said linkage member in order to yieldingly urge said linkage member in one direction, wherein said second lever is in operative engagement with said linkage member in a manner resulting in said first mentioned lever and said second lever being urged in rotative motion relative to each other, abutment means carried by one of said levers to prevent said relative rotative motion, wherein said first spring means is effective during normal operation to exert a resilient return force against said linkage member in order to rotate said linkage member said levers and said throttle valve to said idle position.
 11. Apparatus according to claim 10, wherein said linkage member is pivotally connected to said first mentioned lever, wherein said second lever includes a slot-like opening formed therein for the reception therethrough of said linkage member, and wherein said second spring means comprises a coiled torsion spring situated generally between said levers and having opposite arm-like end portions respectively engaged with said levers.
 12. Apparatus according to claim 1, including a second lever pivotally carried by said first mentioned lever, wherein said second spring means is carried by said first mentioned lever in a manner so as to have one end of said second spring means operatively engaged with said first mentioned lever and a second end operatively engaged with said second lever so as to tend to cause said second lever to pivotally rotate on said first mentioned lever, and wherein said latch-type restraining means comprises a recess formed through said second lever and said first mentioned lever, said recess being formed at a distance from pivot means pivotally connecting said second lever to said first mentioned lever, and including a restraining portion carried by said first spring means for engaging said recess thereby providing a resilient force to said first mentioned lever tending to rotate said first mentioned lever and said throttle valve to said idle position and at the same time preventing pivotal rotation of said second lever about said pivot means, said second end of said second spring means being effective upon failure of said first spring means to cause pivotal rotation of said second lever about said second pivot means until said second lever strikes an associated abutment and then being effective to apply a torsional reaction force against said first mentioned lever in order to urge said first mentioned lever and said throttle valve to said idle position.
 13. Apparatus according to claim 1, wherein said second spring means is of a preload and rating sufficient to exhibit a greater force to return said shaft and throttle to said idle position than that exhibited by said first spring means.
 14. A carburetor for an internal combustion engine, comprising a carburetor body, an induction passage formed through said body, throttle shaft means extending through said induction passage and journalled for rotation in said carburetor body, a throttle valve situated within said induction passage and carried by said shaft means for rotation therewith, a first lever fixedly secured to said shaft means for rotation therewith, a first pivot member carried by said first lever and extending generally parallel to said shaft means, a second lever carried by said shaft means in a manner permitting said second lever to be freely rotatable with respect to and about said shaft means, a third lever pivotally connected to said first pivot member so as to at least have one end freely swingable thereabout, a generally cylindrical drum carried by said shaft means, manually actuated throttle control linkage means pivotally connected to said second lever, a first latching surface formed on said second lever, a second latching surface formed on said third lever, a first throttle return spring connected to said one end of said third lever, said first throttle return spring being normally effective to cause operative engagement between said first and second latching surfaces in order to effectively lock said second and third levers to each other, said first throttle return spring being further normally effective to rotate said shaft means and said throttle valve to an idle position whenever control over said shaft means and throttle valve is relinquished by said manually actuated throttle control linkage means, coiled torsion spring means carried generally about said drum, said coiled torsion spring means having a first arm portion operatively engaged to said first lever and a second arm portion operatively engaged to said second lever, said torsion spring being further effective to continually urge against the effective resistance of said first spring the disengagement of said second and third levers from each other, and said torsion spring being further effective upon failure experienced by said first spring to cause relative rotation between said first and second levers in order to thereby cause rotation of said shaft means and said throttle valve to said idle position.
 15. A carburetor according to claim 14, wherein said shaft means comprises first and second shaft portions, wherein said throttle valve is carried by said first shaft portion, wherein said first and second levers are carried by said second shaft portion, including clutch means carried by said first and second shaft means for effecting driving engagement therebetween, and including means responsive to engine speed operatively connected to said first shaft portion, said means responsive to engine speed being effective upon attainment of a predetermined engine speed to rotate said first shaft portion and said throttle valve some distance toward said idle position. 